Rheostat



Jan. 15 1924.

G. A. REA'M RHEOSTAT Filed March 5. 1921 INVENTOR.

A TT ORNEY.

Patented Jan. 15, 1924..

PATENT OFFICE.

GORDON A. BEAM, 0I' DETBQIT, MICHIGAN.

RHEOSTAT.

Appunti ma umn 5, 1921. semi m. 44a-,045.'

To all 'whom it mary concw'fn.:

Be it known that I, GORDON A. Rmx, a citizen of the United States, residin at Detroit, county of Wayne, State of ichigan, have invented a certain new and useful Improvement in Rheostats; and declare the following to be a full, clear, and exact description of the same, such as will'enable others skilled in the art to which it pertains to make and use the same, reference being had to the accompanyino drawings, which form a part of this speciiication.

This invention relates to electric rheostats and the object of the invention is to provide an improved rheostat comprising two distinct, rheostatic elements, one which may be conveniently termed the main resistance element for varying the resistance in the circuit by a series of steps and the other which will be hereinafter -termed the secondary resistance element by means of which the resistance between steps may be finely adjusted. A further object of the invention is to provide an electric rheostat in which the main and secondary resistance elements are arranged in two concentric circles and the movable Contact members ofthe rheostat are pivoted on the common center of the main and secondary resistance elements. A still further object of the invention is to provide an electric rheostat in which both contact members are operable by a single knob the construction being such that upon a turn of the knob in one direction the resistance in the circuit is increased means being provided whereby the full resistance of the secondary resistance element is placed in the circuit when the main contact member is turned to increase. the resistance in the circuit, means being also provided whereby the resistance of the secondary resistance element is cut out ofthe circuit upon actuation of the knob to decrease the resistance in the main resistance element, the resistance in the secondary resistance element being adjustable at all times without disturbing the position of the main contact member on the main resistance element. These objects and the several novel features of the invention are hereinafter more fully described and claimed and the preferred form of construction by which these objects are attained is shown in the accompanying drawings in which- Fig. 1 is a plan view of an electric rheostat embodying my invention.

Fig. 2 is a section taken on line 2-2 of Fig. 1.

Fig. 3 is a perspective view of the auxiliary resistance element and the insulating block to which it is secured.

Fig. 4 is an elevation of my invention as applied to the sliding type oi* rheostat.

s shown in Figs. 1 and 2, a base 1 is provided which is a non-conductor of electricity such as porcelain2 hard rubber or the like. This base 1 is rovided with an arcuate groove 2 in which 1s mounted the main resistance element 3. The main resistance element consists of a core 4 which is made of insulating material and wound about this core is a resistance coil 5. The resistance element 3 is provided with a metal contact 6 which is connected to the resistance coil 5 and is also connected by a metal strip 7 to the terminal 8. As shown more particularly in Fig. 2, pivotally mounted in the center of the base 1 is a shaft 9 having a knob 10 on the upper end thereof. Rotatably mounted on the shaft 9 is an insulator block 11, shown more particularly in Fig. 3, which is provided with a main contact member 12 secured thereto and adapted to contact the different turns of the resistance coil 5. Connected at 13 to the contact member 12 is a. secondary resistance element 14,v

the exposed face of which is equal in resistance to a single turn of the resistance coil 5. Secured to the shaft 9 by the nuts 15 and 16 is asecondary contact member 17 adapted to contact the secondary resistance element 14. It will be noted more particularly Figs. 1 and 3 that the insulator block 11 1s provided with a cut-away portion provlding shoulders 18 and 19 limiting the movement of the contact member 17 about the periphery7 of the insulator block. Beneath the insulator block 11 and in contact with the shaft 9 is a metal plate 20 which extends and contactsthe terminal 21 of the rheostat.

In operation a pair of lines 22 and 23 are provided from a suitable source of current supply and are connected to the terminals 8 and 2]., With the device in the position shown in Fig. 1 it will be seen that the current How is through' the Wire' 22, terminal 8, metal strip 7, contact member '6, resistance coil 5,.tl1ence through the main contact member 12, through the secondary resistance element 14, secondary' contact member 17, shaft 9 and through the plate 20 to the terminal 21. To set the device to provide ay certain amount of resistance in the circuit the knob 1f) is turned to the right which causes the secondary contact member 17 to engage the shoulder 18 of the insulator block 1l and thus move the main contact member 12 over the resistance coil 5l This member 12 is Ilto* be turned until slightly too much `resistance is placed in the circuit whereupon by turning the knob 10 to the left the resistance ot the auxiliary resistance element is reduced until the desired amount of resistance is placed in the circuit. To further reduce -the resistance in the cir cuit the knob 1() is turned to the left until the secondary contact member 17 vengages the shoulder 1S) of the member 11 at which time lthe secondary resistance is cut out of the circuit and by further turning the knob 10 to the left the `main contact member 12 is turned to lessen the resistance in the subdivided rcsistance clement. In this case the member 12 is to be turned until there is less resistance than desired in the l circuit at which time by again turning the knob 10 to the right the secondary contact member 17 is moved over the secondary resistance elethan required and thenL reduce the re-v sistance to the desired amount by moving the contact member 17y to reduce the resistance of the secondary resistance element. It can also be seen that to reduce the resistance in the circuit toI any appreciable extent it is necessary with this device to` first cut out the secondary resistance and then turn the pointer until slightly less resistance than is necessary is included in the circuit at which time the secondary resistance may be increased by moving the secondary contact member over the secondary resistance element. By this construction the main contact member may be positioned on the main resistance element to include approximately the resistance required at which time the exact resistance required may be.

included inthe circuit by adjustment of the secondary contact member on the secondary resistance element, the secondary resistance element beingl equal to the resistance between the turns or steps of the main resistance element.

In Fig. 4 I have illustrated my invention as applied to the sliding type of rheostat and have provided a 'base 1a of insulating 'apertures through which the rod 6a extends.

rllhis member 7a supports a secondary resistance element 10a which is equal in resistance to one of the turns or steps of the main resistance coil 3a. Connected to this resistance element 10a at 11a is a main contact member 12a which is adapted to contact different turns of the main resistance element 3, Mounted on the bar 6a and in electrical contact therewith is a member 13a having 'a knob- 14a by which the member 13a may be moved along the rod 6a, between the uprights' 8a and 9u of the member 7 a. This member 13n is provided with a secondarycontact member 15a which is in contact with the secondary resistance element 10a at all ti'mes. A pair of Wires 16n and 1'?a vare provided, and connected With a suitable source of current supply, the Wire 17a being connected to the resistance coil 3Et and the Wire 16a being connected to the rod 6a as shown.

In this device the current passes through the Wire 17a, coil 3., main contact member 12a, secondary resistance element 10, secondary contact member 15a, member 13EL and through the rod 6a to the Wire 16a. In operation to increase the resistance the inember 132l is moved by means of the knob 14 to engage the upright 9 of the member 72*l which throws the resistance of the secondary resistance element 1()EL into the circuit. To further increase the resistance the member 13a is moved further to the left which moves the member 7a and main contact member 12a until a slightly greater amount of resistance than necessary is placed in the circuit at which time by moving the block 13a to the right the resistance o the secondary resistance element may be decreased so that the total resistance is the amount rei .resistance than require is concluded in the circuit at which time by moving the member 13 to the left the total amount of resistance mayl be increased by the member v15l on the secondary resistance element 10 to the required amount. It can thus be seen that the operation of either of the devices shown in Figs. l or 4 is fundamentally the same the difference being more particularly in the adaptation of the invention to the different types of rheostats.

From the foregoing description it becomes evident that the device is very simple and efiicient in operation, of comparatively low manufacturing costand provides a rheostat of very line adjustability, which will not easily get out of order and which accomplishes the objects desired.

Having thus fully described my invention, its utility and mode of operation, what I claim and desire to secure by Letters Patent of'the United States is- 1. In a rheostat, a main resistance element, a secondary resistance element, an insulator block on which the secondary resistance element is carried, a contact member for the main resistance element carried on the said block, a shaft on which the block is mounted, a contact member for the secondary resistance element supported on the said shaft.

2. In a rheostat, a main resistance element, a secondary resistance element, an insulating block on which the secondary resistance element is mounted, a contact member for the main resistance element secured to the said block and electrically connected to the said secondary resistance element, and a contact member for the said secondary resistance element movable thereover.

3. In a rheostat, a subdivided resistance clement, a contact lnember adapted to make connection with the points of subdivision thereof, secondary resistance element electrically connected with the first named contact` member, a contact member for the secondary in the base concentric to the said arc a knob for turning the shaft, a)b1ock rotatably mounted on the said shaft, a Contact member for the sub-dividcd resistance element carried thereby, a secondary resistance element .carried on the said block and in electrical contact with the contact member for the sub-divided resistance element, the said lblock being notched on one side, the

secondary resistance `element being exposed in the said notch, and a contact member,

secured to the said shaft and engaging the exposed portion of the secondary resistance element.

5. In a rheostat, a base, a sub-divided resistance element mounted thereon, a contact member for makin circuit connections to the points of sub-division thereof, ashaft rotatably mounted in the base concentric to the sub-divided resistance element, an insulator block rotatably mounted on the said shaftand providing a mounting for the contact member, a cut-away portion on the said block, a secondary resistance element electrically connected to the contact member and exposed to the said cut-away portion, the exposed portion ofthe secondary resistance meinberbeing substantially equal in resistance to one of the'sub-divisions of the sub-divided resistance element, and a second contact member secured to the said shaft and making continuous circuit connection to the secondary resistance element, and extending into the cut-away portion of said block providin a turning means therefor at the limit o movement of the contact member in either direction.

cation.

GoRDoN A. BEAM. 

